Problem rendering additional scenes
I managed to work out the issue.
It’s a user error rather than a blender issue.
I found that when I created the first copy I had a clip in the video editor, which then got copied across to the new scenes.
I didn’t spot it because I’d deleted the clip from the video editor after I’d made the scenes.
Soon as I removed the clip , then the renders started working again.
Interesting lesson learnt lol